Cell Cycle Flashcards
what is cell proliferation ?
- cell grows + divides to produce 2 daughter cells
what are the three main types of cells (growth) ?
- labile cells
- stable cells
- permanent cells
what are labile cells + example ?
- constantly dividing
- epithelial cells
what are stable cells + example ?
- low rate of division normally but can rapidly divide in response to injury or stimuli.
- eg. hepatocytes
what are permanent cells ?
- permanently differentiated so unable to divide
- eg. neurons
what is an example of illness with decreased proliferation and increased cell death ?
- chronic wound
what is an example of illness with increased proliferation and decreased cell death ?
- cancer
what are the 3 stages of the cell cycle ?
- Interphase
- Mitosis (nuclear division)
- Cytokinesis (cytoplasm division)
what are the stages of interphase ?
- G1 phase (gap 1 )
- S Phase
- G2 phase
what happens during the G1 phase ?
- cell grows before DNA synthesis
- synthesizes proteins + organelles
what happens during the S Phase ?
- DNA replication
what happens during the G2 Phase ?
- after DNA synthesis, lasts until cell division
what is G0 phase ?
- cells can enter G0 from G1 if conditions aren’t favourable
- resting phase
- do not divide
what cells are permanently in the G0 Phase ?
- nerve cells
what are the 5 Phases of Mitosis ?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
what happens during prophase ?
- chromosomes condense
- nucleolus disappears
- centrioles move to opposite poles
what happens during prometaphase ?
- spindle fibers / micro tubules attach to centromere
- chromosomes fully condense
what happens during metaphase ?
- chromosomes align at equator
what happens during anaphase ?
- centromere divides
- sister chromatids are pulled to opposite poles
what happens during telophase ?
- nuclear membrane reforms
- chromosomes decondense
what happens during cytokinesis ?
- cytoplasm divides
- 2 daughter cells produced
what is the role of G1 checkpoint ?
- checks if cell is large enough
- if environment is favourable
- checks DNA for damage
what is the role of the
G2 checkpoint ?
- checks duplicated DNA for any damage
- checks cell size
what is the role of the M (metaphase) checkpoint ?
- checks all chromosomes are aligned and attached to spindle fibers
How CDK’s (Cyclin Dependent Kinases) activated ?
- Cyclin binds to CDK exposing its active site
- protein substrate and ATP bind to CDK active site
- protein substrate is phosphorylated
- phosphorylated protein regulates cell cycle at different stages
Phosphorylation of Rb protein?
- mitogens activate cyclin D
- Cyclin D binds to CDK 4/6
- CDK 4/6 phosphorylates Rb protein
- Rb protein is attached to E2F (transcription factor)
- phosphorylation of Rb inactivates it
- E2F is released and switches on cell cycle
